Welding gun



Dec. 14, 1948. H. BERONIUS 2,456,105

WELDING GUN Filed Feb. 2a, 1947 (Ittornegs Patented Dec. 174, 1948WELDING GUN Harry V. Beronius, Detroit, Mich., assignor to WeldingMachines Manufacturing Company, Detroit, Mich., a corporation ofMichigan Application February 28, 1947, Serial No. 731,539

3 Claims.

This invention relates to welding equipment and in particular to weldingguns for spot welding.

One object of this invention is to provide a welding gun having amovable plunger connected to the welding electrode and means for'improving the electrical contact between the plunger and the gun inwhich it reciprocates.

Another object is to provide a welding gun as set forth in the precedingobject wherein means is provided for forcibly moving the plunger and theadjacent portion of the welding gun into more intimate contact with oneanother at the end of the stroke, thereby decreasing the resistanceoffered to the passage of the welding current and consequently reducingthe heating effect within the gun while increasing the eiiiciencythereof.

Another object is to provide a welding gun, as set forth in thepreceding objects, 4wherein the welding electrode is attached to ahollow plunger which reciprocates relatively to a hollow split stem andwhich contains an auxiliary plunger for spreading the walls of the stemapart so that they more rmly engage the inner wall of the f hollowplunger, thereby enhancing the electrical contact between them andcorrespondingly reducing the resistance offered to the passage of thewelding current between the stem and the plunger.

Other Objects and advantages of the invention will become apparentduring the course of the following description of the accompanyingdrawings, wherein:

Figure 1 is a side elevation, partly in central vertical section,through a welding gun, according'to' a preferred form of the invention;

Figure 2 is a right-hand side elevation of the welding gun shown inFigure 1;

Figure 3 is a horizontal cross-section through the welding gun takenalong the line 3-3 in Figure 1;

Figure 4 is a horizontal cross-section through the welding gun takenalong the line 4-4 in Figure 1, showing details of the split stem;

Figure 5 is a horizontal cross-section through the welding gun, near thebottom thereof, taken along the line 5-5 in Figure 1 and showing thepassages for pressure iiuid and for cooling liquid respectively; and

Figure 6 is a diagrammatic side elevation showing the welding gun ofFigure 1 in use between a. pair of abutments, for welding a pair ofmetal sheets.

Hitherto, in welding guns for spot weldingaoperations, it has beencustomary to move the welding electrode into contact with the workpiecesby means of a plunger reciprocating in a cylinder supplied with pressurefluid, either hydraulic or pneumatic. In such welding guns the contactbetween the plunger and the walls of the cylinder is relied upon tofurnish a part of the path over which the electric welding current runson its way to the electrode. -Since the plunger moves relatively to thecylinder, however, the contact between them is at best ineicient becausethe plunger must reciprocate freely in the cylinder and accordingly asuiiicient clearance must be provided,

Since the welding current is of a very low voltage, even though of ahigh amperage, it does not easily cross the gap between the cylinder andplunger without causing resistance which results in heating up the gun.This heat interferes with the efficiency of the gun and reduces theamount of current reaching the welding electrode. Where a non-conductinglubricant such as oil is employed in the cylinder for lubricating theplunger, this oil still further increases the resistance to the passageof current and thus still further reduces the eiciency of the weldinggun.

The present invention solves this problem by providing means for forcingthe plunger and cylinder into more intimate contact with each otherafter the completion of the stroke of the plunger, so that a greatlyimproved electrical contact is obtained between the cylinder andplunger. Any lubricant used is squeezed out of the space between thecylinder and plunger and the eiiiciency of the gun is still furtherincreased. In this manner, the electrical resistance is reduced andconsequently, the heating effect thereof is likewise reduced.

Referring to the drawings in detail, Figure 1 shows a welding gun,generally designated IU, according to a preferred form of the inventionas consisting of an electrode holder II having a threaded bore l2 forreceiving the threaded end I3 of a hollow welding electrode I4 having anend I5 which is to be brought into contact with the work piece. Theelectrode I4 is provided with an internal cavity I6 opening into thebore I2 and a coolant pipe I1 extends downward into the cavity I 6 andpasses through a passageway IB and has a, head I9 iitting into an inletport 20 (Figure 5) which in turn is connected to a coolant supply line(not shown). The electrode holder is also provided with a coolantdischarge passagewayvZl (Figures 2 and 5) opening into the bore 2 andhaving an outlet port 22 connected to a coolant discharge line 23 forcarrying away the coolant liquid, such as water, which has been heatedup during the process of cooling the electrode i4.

The electrode holder il is also provided with an upwardly extendingcylindrical plunger portion 24 and"contains:zafpressurefiluidfpassageway25 leadin'gitofanoutlet port .26 Whichiisf'connected by the coupling 21to a fluid pressure supply line 28. The passageway 25 opens into thelower end of the plunger bore 29. Theputer Wall of the hollow plunger 24passes through an opening an in the bottomlofxafcylinder 3l and has acoil spring 3Q abutting -the-rlowerfend Wall 33 of the cylinder bore 34(Figurel). The upper end of the hollow plunger.24is .threaded as at 35to receive a retaining ring v36 which serves as an abutment for theupper end-ofthe coil spring 32 and also slidably engages the cylinderboref34.

:The upper-tend .of i the cylinder t.boree'34 -is :providedv/ith aan.annular-groove 31 for v.receiving a snap ring (Figures 1 .and 53) the..inner rim :of whichis seated-in an annularirecess l39 vin .the head1-4Qoflahollow steni'fdL Therstem l4| -ihas anfouter -fwall 42fsnuglyfitting the innerib'ore 29 `ofthe hollow? plungerfll .y-et with asucient clearance to fperrnit the p plunger' 24 to. reciprocate freelyalong the stein 4 i.

The wstem .4l is .provided fwith :an internal longitudinal bore or"recess f43, i the yside walls Aof which'are provided with I slots 44:forming l fingers 45 extending downward to the lowerend of fthe stem4i,the'.latter bei'ng-provided'withwa beveled seatfitrat' that point.Fitting into andvmating with the yconical seattet is 4the conicalthead-41' of fanrauxiliary plunger 4t2 1 (Figure. 1) which :reciprocatesin ythe inn-eri boreY 42 of .the plunger e 24. The f auxiliary 'plunger43 y'is '.provded iwith fan, annular groove# itil/having' Aa sealingringorpackingrringrll seated therein. Thefpacking ringfS is-of .any.yielding :or :resilient material such as synthetic rrubber. ATheauxiliary plunger 43 v.is also provided :with La reduced :diameterportion lf extendingdowmvardand engageable 4with :the bottom wall 52 ofthe plunger bore 42. The head vwill fof the :stem uil is :provided .witha threadedbore :53 at the top vthereof zfor `receiving the threaded.fshankiofa :capscrew:f54, the latter: serving 'fas an;l abutment-whichmayfeasily be replaced when itis dented, worn, f or f'xotherwisedamaged.

vThe electr-ode holder Il'isgprovided with an offset 'shelflike .portion"55 "which :tcontains the fluid 'pressure passageway :25 land port :2l:and which also'has'fa dat' upper surface-.towhichithe end.58ofazhandleflis attached, as `by screws 60, The upper endofthefhandleriisgprovided with fan enlargement or boss .5i havngaf'cavity F62 therein :for receiving a "pushbutton switch 53 operated.by a push button v1.641 and 'held l:in position by fa yset lvscrew "65.threaded tinto -.the transverse hole .266. The vboss `r-6I .is falso.provided `with a transverse .hole"61 2through 4'which a i conductor i`cable rta with .conduct-ors :69 s and 1 0 therein *enters the cavity.The rconductors 69 and '10i are 'connected fto' th'eiterrninalsofthepushzbutton'switch L63 and'sattheir oppositeen'ds are connected -.to daYconventional vremote 'control mechanism (not shown) Athe details -of:which form norpartfoft-thepresent invention. Thisremotecontrolinechan-ism is loperated .by .the depressingr ofathepush button@3f to'eperateaa'valve which admits .pressure fluid .through f thesupply 39 surrounding the head 40 is below the level of theannularrecess 31. While the parts are in -`this position, the snap ring 3B ispushed down .intol-tlretcylin'd'er=.bore 34 until it snaps into the'1115i .'isueleased'andmoves upward until its annular .shoulder 39-engages the snap ring 38.

recessfsSLV-tvhereupon the head 4U of the stem 4l Thisconstruction'holds'these parts in assembly.

Operation 'fnithefoperztion ofithelinventiong-the gun Ii) is Aordinarily'..used rwith the upper :surface 12 of the cap screw 54 in engagementwith .a rilxed upperfa'butment .1.3 CCFigure-i) which islpreferably iinsulated by Lan i insulating slayer '14 rfromm supporting abutmentsl..Theiwcrkftgforeexampleflthinffsheetsf of @metal Yil and :1,8 which *areintended--to'be welded, '.is :placed upon a ilower abutment ''1i9 whichfis 'insulated by fla :layer 1. of insulating material ..80 :from:alower support 8|. The two abutments 113 fand leifare ziconnected Lbyconductors F32 .fand 83 respectively to the `winding 84 of= one #coilfof 1 a1we'lding :transformer @85, the other fco'ilda 'of which is.connected' by i. oonductors 31ffanzd'BStOHaf-source'of electriccurrent.

v'To iwel'd 1 the 1wo'ikpieces l' and 18, these tare placed upon theabutment :19 land `the `Awelding gun I moved into position between 'theTabutments 13 and 519. 'The v.welding v:transformer .35 is energizedfbyconnecting .thev conductorsitilL-:and 88 "to la 'source 'of --electriccurrent. Meanwhile, cooling l`watertis lcaused to flow .into :the".port' '-20 (Figure 5) andzdownward*through the :tube ft`1 into 'theelectrode "recess it and :thence fout through fthe 'port 12 2 `and 'pipeZ3. '.The operator now v dep'resses 'fthe 'push -1 button .64 of yithe:push button @switch "t3, setting I the remote lcontrol mechanism inoperation Ivto cause pressure huid, such as compressed fair for y:oil lor v:water :runder pressure, to pass through thefsupply'pipe :28intofthe f plunger 'bore 2 9.

"The" pressureffluid acting between therannular surface 49 atL thebottom of the fauxiliaryl'lunger 48 and the surface 52 at the endo'ff'the `hollow plunger 2'4 forcesfthelatter 'downward andfcarr-iesWithit the electrode t4. v--Mea'nwhile'thefauxiliary plunger :"4'8flis'-temporarily'held immovableby the engagement oflthefcap-screwfltintheh'ead of th'e stem 4I with the upper abutmentl.

.When the :electrode i4 f encounters the `workpiec'es f11:=and T18, itIforces -them `firmly -Iltogether and halts. This causes the pressure torlseln the iplunger 'bore 22S, anti this :pressure acts 'Sion thelowerffend 'ci theauxiliaryplunger i453,5 forcing its conical headportionwl' upwardV into theconical'fseatf 4B. 'Thisfwedgeelike action inturny forces the: fingers -245 rapart; pushing ztheirzouter.surfacesnrmly into engagement .with -the Rwa'lls .Lof Athe plunger bore '42y.'fsqueezing tout .any lubricant which may be on the walls thereof.Thissaction spans `the `egap which vis the normal -iclearance necessary.ifor free '.zreeiprocation between the hollowplungerf 241r andthe's'temfll lfandrbringsathe fingers 45 into more intimate electricalcontact with tthelplunger #24. .The iwelding current then passes freelybetween the abutments 13 and 19 by way of the Welding gun I!! and itselectrode I4 while the workpieces 'll and 'i8 are strongl;T compressed,spot-welding these to each other.

By thus effecting a rmer engagement and more intimate electrical contactbetween the fingers 45 of the stem 4l and the inner Wall of the hollowplunger 24, the resistance offered to the flow of current is greatlyreduced and the eiliciency of the welding operation correspondinglyincreased. This also greatly reduces the heating of the gun, whichpreviously occurred from the resistance caused by the necessity for thewelding current to cross the gap between the cylinder and plunger of thewelding gun.

What I claim is:

1. A welding gun comprising a pair of relatively reciprocable structuresconnected in series with the welding current circuit, a holder for aWelding electrode connected to one of said structuresa fluid pressuremotor including relatively reclprocable tubular plunger and cylinderelements operatively connected respectively to said structures forreciprocating said structures relatively to one another to engage theelectrode in said electrode holder with the Work to be Welded, anexpansible tubular stem connected to said plunger element and projectingtelescopingly into said tubular plunger element, said stem and saidplunger being of electrically-conducting material and an auxiliarypiston reciprocably mounted in said tubular plunger element in expandingrelationship with said stem, one of said structures having a fluidpassageway therein communicating with th'e interior of said tubularplunger and responsive to the supplying of pressure fluid thereto formoving said auxiliary piston into engagement with said stem andexpanding said stem into enhanced electrical contact with said plunger.

2. A welding gun comprising a pair of relatively reciprocable structuresconnected in series with the welding current circuit, a holder for aWelding electrode connected to one of said structures, a iluid pressuremotor including relatively reciprocable tubular plunger and cylinderelements operatively connected respectively to said structures forreciprocating said structures relatively to one another to engage theelectrode in said electrode holder with the Work to be welded, anexpansible tubular stern connected to said plunger element andprojecting telescopingly into said tubular plunger element, said Stemand said plunger being of electrically-conducting material and anauxiliary piston reciprocably mounted in said tubular plunger element inexpanding relationship with said stem, one of said structures having afluid passageway therein communicating with the interior of said tubularplunger and responsive to the supplying of pressure uid thereto formoving said auxiliary piston into engagement with said stem andexpanding said stem into enhanced electrical contact with said plunger,said piston and the adjacent end of said stem having mutually engagingmating conical portions thereon.

3. A Welding gun comprising a pair of relatively reciprocable structuresconnected in series with the welding current circuit, a holder for aWelding electrode connected to one of said structures, a iiuid pressuremotor including relatively reciprocable plunger and cylinder elementsoperatively interconnecting said structures for reciprocating saidstructures relatively to one another to engage the electrode in saidelectrode holder with the Work to be welded, one of said elements havinga longitudinally split portion projecting therefrom and an auxiliarypiston in said motor, said piston and the adjacent end of saidlongitudinally split portion having mating conical portions responsiveto the supplying of pressure fluid to said motor for forcibly urgingsaid last-mentioned element into enhanced electrical contact With theother element.

HARRY V. BERONIUS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,233,897 Nichols Mar. 4J 19412,293,337 Harris Aug, 18, 1942 2,314,320 Van Eck Mar. 16, 1943

